Chapter 8 - The Skeletal System

Bones form the body's supporting framework. The hard structure of bones protect delicate structures enclosed within them. The skull protects the brain; the breastbone and ribs protect the heart and lungs.

Bones; as muscles contract, they pull on bones and move them.

Calcium storage; bones help maintain homeostasis of blood calcium. necessary for nerve and muscle function.

The process of blood cell formation is carried on in the red bone marrow.

• long - humerus
• short - carpals 
• flat - frontal 
• irregular - vertebrae

A round bone like kneecap

Hollow tube of hard compact bone

Inactive, fatty form of marrow found in adult skeletons.

Hollow space inside the diaphysis that contains yellow marrow

Made of spongy bone that contains red bone marrow

Thin layers that cover each epiphysis; provides a cushion

Strong, fibrous membrane covering bone everywhere except at joint surfaces

Thin membrane that lines medullary cavity

On the inside of the thin layer of compact bone.

Bony trabeculae

Bone and cartilage

To create red blood cells

• Texture from needlelike threads of bones called trabeculae surrounded by network of open spaces
• Found in epiphyses of bones 
• Spaces contain red bone marrow

• Structural unit is an osteon-calcified matrix arranged in multiple layers or rings called concentric lamella 
• Bone cells, called osteocytes, are found inside spaces called lacunae, which connected by tiny tubes canaliculi
• Covered by periosteum

Mature bone cells that are made from the active bone building cells called osteoblasts

Small passageways or canals that contain cytoplasmic extensions of the osteocyte

Little spaces between the hard layers of the lamellae

concentric lamella, lacunae, canaliculi, spongy bone

Blood vessels

It is spongy because marrow is made and stored there

It rebuilds slowly because it lacks blood vessels

˜flexible gel-like substance and lacks blood vessels

multinucleated cells that remove bone

bone-forming cells

mature bone cells that are located in the lacunae of compact bone

• It is the process of forming bones from cartilage models
• ˜Center of ossification first appears in diaphysis˜
• Centers of ossification then develop in epiphyses
• ˜Epiphyseal plate of cartilage between epiphyses and diaphysis remains until skeletal maturity
• Epiphyseal line (bone) replaces epiphyseal plate (cartilage) when growth ceases

Enochondral ossification and flat bones (i.e. skull bones) form in connective tissue membranes by another process

When all epiphyseal cartilage has become bone

“Remodeling” a growing bone as it changes from a small cartilage model to an adult bone requires continuous activity by osteoblasts.

The process of “sculpting” by osteoblasts and osteoclasts allows bones to respond to stress and injury by changing size, shape, and density

They form new bone by laying down organic material, followed by calcium salts

Strength to support the weight of the body; balance necessary to stand erect and walk on two feet

The sternum

The first seven pairs of ribs are called true ribsand are attached to the sternum. The eighth, ninth, and tenth ribs are attached to the cartilage of the seventh pair of ribs; they are called false ribs. The last two pairs of ribs are not attached to costal cartilage; they are called floating cartilage.

The humerus is attached to the scapula at its proximal end and articulates with the two bones of the forearm at the elbow joint.

The bones of the forearm are the radius and ulna.

The bony process of the ulna, called olecranon process, fits into the olecranon fossa and makes movement possible.

• The axial which consists of 80 bones, the skull, spine or vertebral column and thorax. 
• The appendicular system which consists of 126 bones, the upper extremities, including shoulder (pectoral) girdle and the lower extremities, including the hip (pelvic) girdle.

• Subdivision of the skeletal system 
• Four normal curves
• Three abnormal curves 
• Lordosis or "swayback"
• Kyphosis or "hunchback"
• Scoliosis

The skull consists of eight bones that form the cranium, fourteen bones that form the face, and six bones in the middle ear. The two parietal bones that give shape to the topside of the skull form immovable joints, called sutures, with several bones: the lambdoidalsuture with the occipital bone, the squamous suture with the temporal bone, and the coronal suture with the frontal bone.

• Cervical (7 bones)
• Thoracic (12 bones)
• Lumbar (5 bones)
• Sacrum (1 bone)
• Coccyx (1 bone)

• 12 pairs of ribs
• Sternum or breastbone
• Thoracic vertebrae

• True ribs (ribs 1-7)
• False ribs (ribs 8-10)
• Floating ribs (11-12)

61% of the human body's bones (126 out of 205) are part of the appendicular skeleton.

• Bones in shoulder or pectoral girdle connect bones of upper extremity (arm, forearm, wrist, and hands) to axial skeleton
• Bones in hip or pelvic girdle connect bones of lower extremity (thigh, leg, ankle, and foot) to axial skeleton

Shoulder or pectoral girdle formed by: scapula, clavicle (frequently fractured), arm - humerus, forearm - radius and ulna, wrist - 8 carpal bones, hand - 5 metacarpal bones, fingers - 14 phalanges or finger bones

Hip or pelvic girdle formed by the two coxal or pelvic bones (one on each side) with sacrum and coccyx behind

Each coxal bone in infant consists of separate ilium, ischium, and pubic bones—bones are fused into a single coxal bone in the adult

acetabulum

femur

• Patella or kneecap articulates with femur and tibia
• Lower leg—tibia (“shinbone”) and fibula

• 5 metatarsal bones
• 7 tarsal bones (calcaneus or heel bone is largest tarsal)
• 14 phalanges or toe bones
• 3 arches of foot—2 longitudinal (medial and lateral) and a transverse or metatarsal arch—if weakened, result is “flat feet”

• size, shape of pelvis, size of pelvic inlet and pubic angle. 
• In general, the female pelvis can accommodate the body of a fetus before birth and allow it to pass through it during birth. Male hipbones are generally larger and narrower than the female’s.

the hyoid - the bone in the neck to which the tongue is anchored

• Synarthrosis (no movement)—fibrous connective tissue grows between articulating bones (for example, sutures of skull)
• Amphiarthrosis (slight movement)—cartilage connects articulating bones (for example, symphysis pubis)
• ˜Diarthrosis (free movement)—most joints belong to this class

Joints hold the bones together securely and at the same time make it possible for movement to occur between the bones

Synarthroses are joints in which fibrous connective tissue grows between the articulating bones, holding them close together. The joints between cranial bones are synarthroses. Amphiarthroses are joints in which cartilage connects the articulating bones. The joints between the bodies of the vertebrae are amphiarthroses. The joints make it possible to flex forward, sideways, and to rotate

ball-and-socket, hinge, pivot, saddle, gliding, and condyloid

ball-and-socket joints (shoulder and hip)

Flexion and extension

carpometacarpal joint of thumb

• Most common and serious malignant bone neoplasm
• Frequent sites include distal femur and proximal tibia and humerus

• Cancer of skeletal hyaline cartilage
• Second most common cancer of skeletal tissues
• Frequent sites include medullary cavity of humerus, femur, ribs, and pelvic bones

• Characterized by loss of calcified bone matrix and reduction in number of trabeculae in spongy bone
• Bones fracture easily, especially in wrists, hips, and vertebrae
• Treatment includes drug therapy, exercise, and dietary supplements of calcium and vitamin D

shortened stature and classic kyphosis of the thoracic spine

˜both diseases characterized by loss of bone minerals related to vitamins

• Loss of bone minerals occurs in infants and young children before skeletal maturity
• Lack of bone rigidity causes gross skeletal changes (bowing of legs)
• Treated with vitamin D

• Mineral content is lost from bones that have already matured
• Increases susceptibility to fractures
• Treated with vitamin D

• Faulty remodeling results in deformed bones that fracture easily
• Cause may be genetic or triggered by viral infections
• Treated with pain control and drugs that improve the strength of the bone are used

• Bones are brittle because of lack of organic matrix
• Treatment may include splinting to reduce fracture and drugs that decrease cell activity
• Genetic

• General term for bacterial (usually staphylococcal) infection of bone
• Treatment may involve surgery, drainage of pus, and IV antibiotic treatment—often over prolonged periods

The density of bone tissue and slowness of the healing process makes bone infections harder to treat than many other tissue infections

˜Open (compound) fractures pierce the skin, and closed (simple) fractures do not

˜complete and incomplete, linear, transverse, and oblique

open

closed

traumatic injury

• Most common noninflammatory disorder of movable joints—often called “wear and tear” arthritis
• Symptoms: Joint pain, morning stiffness, Bouchard nodes (at proximal interphalangeal joints), Heberden nodes (at distal interphalangeal joints) of the fingers
• Most common cause for partial and total hip and knee replacements

Do not usually involve inflammation of the synovial membrane; symptoms tend to be local and not systemic

It is a fracture where a piece of bone is pulled free from a violent muscle contraction

• Dislocation or subluxation—articular surfaces of bones in joint are no longer in proper contact
• Sprain—acute injury to ligaments around joints (for example, whiplash-type injuries)
• Strain—acute injury to any part of the “musculotendinous unit” (muscle, tendon, junction between the two, and attachments to bone)

• ˜General name for several inflammatory joint diseases that may be caused by infection, injury, genetic factors, and autoimmunity
• ˜Inflammation of the synovial membrane occurs, often with systemic signs and symptoms

It is treated by the use of antibiotics.

• Systemic autoimmune disease—chronic inflammation of synovial membrane with involvement of other tissues such as blood vessels, eyes, heart, and lungs
• Gouty arthritis—synovial inflammation caused by gout, a condition in which sodium urate crystals form in joints and other tissues
• Infectious arthritis—arthritis resulting from infection by a pathogen, as in Lyme arthritis and ehrlichiosis, caused by two different bacteria that are transmitted to humans by tick bites

It is treated by the use of antibiotics.